Hitherto pistons in automotive gasoline engines, have usually had three piston rings, but in order to improve performance and economy the use of two piston rings has recently become a subject of study and development in various field of the art. On the other hand large displacement diesel engines such as used in buses and trucks are usually used to the limit of their effective life in view of economy. In both cases the volume of gas leaking from the combustion chambers of the cylinders into the crank case, i.e. blow by gas, has become an important social problem. Therefore, in the field of the art concerned, in order to solve the problem an accurate measurement of the flow rate of the blow by gases has become an important task. Such blow by gas principally comprises combustion gas, and includes mists comprising water droplets condensed from vapor, minute droplets of lubricating oil, liquid droplets of unburnt fuel, etc.
Although hitherto it has been publicly known to measure the blow by gas by mainly a wet-type gas meter such a measuring method has various problems.
Here for reference, a typical method for measuring blow by gas using a wet-type gas meter will be explained in reference to FIG. 4 of the attached drawings wherein the principle thereof is shown in a block diagram. The principal elements or substances represented by the reference numerals therein are as follows:
1...Blow By Gas; 2...Oil Trap; 3...Surge Tank; 4...Wet-Type Gas Meter; 5...Liquid Discharge Opening.
In a flow rate measuring apparatus constituted by the above elements, the blow by gas 1 discharged from an engine not shown is first introduced into the oil trap 2 having a box-shaped vessel in which the velocity of the gas 1 is made to be substantially zero so that the mists comprising vapor and oil contained in the gas fall by gravity to be accumulated in the bottom of the oil trap 2. The gas which has the mists therein removed by flowing through the oil trap 2 is then fed to the wet-type gas meter 4 in order to have its velocity measured.
The wet-type gas meter 4 is, however, influenced by variation in pressure of the blow by gas caused by variation in the gas pressure within the engine cylinders owing to a large pressure drop in the gas meter 4, resulting in instability in indications of the meter 4. In order to stabilize those indications the surge tank 3 must have a large volume. However, since the wet-type gas meter 4 is a volumetric flow rate meter, as the flow rate becomes large the pressure losses in the meter becomes large. Therefore, in order to obtain a real flow rate from the indication of the meter it is necessary for the indicated value to be corrected for the temperature and pressure of the gas in the gas meter 4. Moreover, since the wet-type gas meter 4 is an apparatus which measures an accumulated flow rate during a set period of time it cannot carry out measurement following the varying flow rate such as during acceleration or deceleration of the engine. Further the range of measurable flow rate of a wet-type gas meter is narrow. Accordingly, it cannot be used for the purpose of measuring the flow rate of blow by gas of engines of various displacements. In particular, the measurement of blow by gas of diesel engines, most of which have a large displacements, e.g. more than 6,000 cc becomes very inaccurate. For example, in a diesel engine used for a many years, in order to check whether or not the inner surfaces of its cylinders have worn without disassembly it is most suitable to measure the flow rate of blow by gas. However, it is impossible to use a wet-type gas meter for this measurement for the above reasons. Further, a large amount of blow by gas is a problem not to be overlooked from the view point of environmental pollution, etc. and for solving this problem also, accurate measurement of the flow rate of blow by gas is indispensable.
As stated above the measurement of the flow rate of blow by gas, particularly, in large diesel engines, which is directly related to pollution problems cannot be carried out accurately by conventional wet-type gas meters. On the other hand a reliable measurement method therefor to replace the conventional one has not been found to date.
Therefore, it is a principal object of the present invention to provide a method for accurately measuring the flow rate of a gas including condensable components, mists, etc. such as a blow by gas that, in consideration of the fact that hitherto an accurate measurement of the flow rate of a blow by gas of an engine over a broad range and in particular, at the time of acceleration and deceleration has not been possible.
It is another object of the present invention to provide a method for measuring a flow rate of a blow by gas in an engine which can serve to determine whether or not the engine is still serviceable.
It is a still other object of the present invention to provide a method for measuring a flow rate of a blow by gas in an engine which is usable for study of the possibility of decreasing the number of piston rings in an engine e.g. from three to two.
It is a still further object of the present invention to provide a method for measuring a flow rate of a blow by gas in an engine which serves to study to prevent the blow by gas from polluting the environment.
It is a further object of the present invention to provide an apparatus for carrying out the method for measuring a flow rate of a gas or a blow by gas in an engine as stated above.
It is still further object of the present invention to provide an apparatus for measuring a flow rate of a gas or a blow by gas in an engine which contains condensable components and mists, and which apparatus allows a more accurate measurement of the flow rate of the gas by maintaining its pressure within the apparatus substantially constant, because if the gas is subjected to a pressure drop during its passage through the apparatus the gas pressure at the inlet into the apparatus becomes higher than that at its exit, providing not necessarily accurate results.